Zf5 input shaft bearing or SMF noise?

[Thelebowski]

So i picked up a 92 7.3 idi with a zf5 and the borg warner 1356. T case looks newer, prev. Owner said its a low mile trans (hmm) and new clutch (this is evident.) its a smf convert, truck has 214xxx miles.
When idling with the clutch pedal out, theres a loud, intermittent chatter. With the clutch pedal in, chatter goes away.
At low speeds in first and second, the noise becomes constant, and louder. Sounds like a gear tooth hitting a cover kinda (not the case).
Everywhere i’ve looked tells me its an input shaft bearing, that if left unfixed it could crack the bell housing, yada yada.
But trans shifts fine, engages easily, clutch is tight, all seems good to go, besides that sketchy ass noise.
Im reluctant to split a trans apart in my driveway and try to figure all that out so, could it just be the SMF clutch making all that noise? Or is it really the worst case? How long can you run it before other things **** the bed?
I got 5-30 motor oil in the trans with a lil friction modifier to try and quiet it down, it worked a little but not much.

 

[Big Bart]

Any chance your inspection cover is hitting the flywheel? Or something is loose in the housing. (That you can pull out of the inspection cover area?)

Maybe check with the previous owner, did he also replace the pilot and throwout bearing?

I have a C6 so no expert on your tranny, but many said these the manuals all make noise till you engage the clutch. (But not while driving.)

Let's see what those with manuals say is normal or not.

 

[MtnHaul]

Does the noise go away with RPM above 1400 or so? My single mass setup makes an infernal racket while idling, but only makes noise in gear if RPMs drop too low. The noise does sound horrible at idle but that's part of the charm.
Also, synthetic ATF is a much better choice for the ZF transmission. I tried non-detergent 30wt and it wasn't worth two squirts compared to ATF, especially in cold weather. I've used both Royal Purple and Amsoil with great results. I would be careful using an oil like 5w-30 that is probably out of spec for the transmission. Ford spec'd ATF not motor oil. Just my .02


And FWIW these transmissions can last a while as I have 366k on original trans and t-case with only a slight clunk going into 3rd gear.

 

[franklin2]

I agree with the others. All you have to do is get it idling and making the noise with the clutch out, and then just press the throttle a little bit to raise the rpm. If raising the rpm makes the noise go away, then it's just gear rollover noise.

You can experiment with the throttle, and see if you can tolerate a higher idle rpm. That is all I did and the noise is a lot quieter. I just went out and raised the idle speed a little bit.

I found also that the stock thin oil was best. It shifts better with the stock oil, and it reaches a higher rpm when it's cold with the stock oil. Higher rpm at idle means less noise.

 

[Thelebowski]

Does the noise go away with RPM above 1400 or so? My single mass setup makes an infernal racket while idling, but only makes noise in gear if RPMs drop too low. The noise does sound horrible at idle but that's part of the charm.
Also, synthetic ATF is a much better choice for the ZF transmission. I tried non-detergent 30wt and it wasn't worth two squirts compared to ATF, especially in cold weather. I've used both Royal Purple and Amsoil with great results. I would be careful using an oil like 5w-30 that is probably out of spec for the transmission. Ford spec'd ATF not motor oil. Just my .02


And FWIW these transmissions can last a while as I have 366k on original trans and t-case with only a slight clunk going into 3rd gear.

Yes! Exactly 1400 it does go away, that makes me feel much better haha. My only concern is coming to a stop, engaged first/second gear under 1400 it’ll sound off but consistently and louder, or yaknow if im chugging around a parking lot it’ll do it intermittently. If i clutch in earlier though, or run it above 14-1500k it goes away so i’ve been doing that as much as possible. I’ll definitely swap back to the mercon atf then, i only got that idea fairy from a different thread haha. Definitely not the bell housing cover or anything loose, i’ve been driving it without it on to eliminate some potential causes.

 

[franklin2]

What I have found also, the smoother your engine runs, the less noise you have. Some of these engines are in different states of tune and wear than others, I think that is why the noise is louder with some trucks than other ones.

 

[IDIBRONCO]

What I have found also, the smoother your engine runs, the less noise you have. Some of these engines are in different states of tune and wear than others, I think that is why the noise is louder with some trucks than other ones.

I'll agree with this. I don't hear any extra noise from mine while it's idling in neutral. I only hear the noise when I'm in gear moving at a low RPM.